// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
// Distributed under the MIT License (http://opensource.org/licenses/MIT)

#pragma once

// multi producer-multi consumer blocking queue.
// enqueue(..) - will block until room found to put the new message.
// enqueue_nowait(..) - will return immediately with false if no room left in
// the queue.
// dequeue_for(..) - will block until the queue is not empty or timeout have
// passed.

#include <spdlog/details/circular_q.h>

#include <atomic>
#include <condition_variable>
#include <mutex>

namespace spdlog {
namespace details {

    template <typename T> class mpmc_blocking_queue
    {
    public:
        using item_type = T;
        explicit mpmc_blocking_queue(size_t max_items) : q_(max_items) {}

#ifndef __MINGW32__
        // try to enqueue and block if no room left
        void enqueue(T&& item)
        {
            {
                std::unique_lock<std::mutex> lock(queue_mutex_);
                pop_cv_.wait(lock, [this] { return !this->q_.full(); });
                q_.push_back(std::move(item));
            }
            push_cv_.notify_one();
        }

        // enqueue immediately. overrun oldest message in the queue if no room left.
        void enqueue_nowait(T&& item)
        {
            {
                std::unique_lock<std::mutex> lock(queue_mutex_);
                q_.push_back(std::move(item));
            }
            push_cv_.notify_one();
        }

        void enqueue_if_have_room(T&& item)
        {
            bool pushed = false;
            {
                std::unique_lock<std::mutex> lock(queue_mutex_);
                if (!q_.full())
                {
                    q_.push_back(std::move(item));
                    pushed = true;
                }
            }

            if (pushed)
            {
                push_cv_.notify_one();
            }
            else
            {
                ++discard_counter_;
            }
        }

        // dequeue with a timeout.
        // Return true, if succeeded dequeue item, false otherwise
        bool dequeue_for(T& popped_item, std::chrono::milliseconds wait_duration)
        {
            {
                std::unique_lock<std::mutex> lock(queue_mutex_);
                if (!push_cv_.wait_for(lock, wait_duration, [this] { return !this->q_.empty(); }))
                {
                    return false;
                }
                popped_item = std::move(q_.front());
                q_.pop_front();
            }
            pop_cv_.notify_one();
            return true;
        }

        // blocking dequeue without a timeout.
        void dequeue(T& popped_item)
        {
            {
                std::unique_lock<std::mutex> lock(queue_mutex_);
                push_cv_.wait(lock, [this] { return !this->q_.empty(); });
                popped_item = std::move(q_.front());
                q_.pop_front();
            }
            pop_cv_.notify_one();
        }

#else
        // apparently mingw deadlocks if the mutex is released before cv.notify_one(),
        // so release the mutex at the very end each function.

        // try to enqueue and block if no room left
        void enqueue(T&& item)
        {
            std::unique_lock<std::mutex> lock(queue_mutex_);
            pop_cv_.wait(lock, [this] { return !this->q_.full(); });
            q_.push_back(std::move(item));
            push_cv_.notify_one();
        }

        // enqueue immediately. overrun oldest message in the queue if no room left.
        void enqueue_nowait(T&& item)
        {
            std::unique_lock<std::mutex> lock(queue_mutex_);
            q_.push_back(std::move(item));
            push_cv_.notify_one();
        }

        void enqueue_if_have_room(T&& item)
        {
            bool pushed = false;
            std::unique_lock<std::mutex> lock(queue_mutex_);
            if (!q_.full())
            {
                q_.push_back(std::move(item));
                pushed = true;
            }

            if (pushed)
            {
                push_cv_.notify_one();
            }
            else
            {
                ++discard_counter_;
            }
        }

        // dequeue with a timeout.
        // Return true, if succeeded dequeue item, false otherwise
        bool dequeue_for(T& popped_item, std::chrono::milliseconds wait_duration)
        {
            std::unique_lock<std::mutex> lock(queue_mutex_);
            if (!push_cv_.wait_for(lock, wait_duration, [this] { return !this->q_.empty(); }))
            {
                return false;
            }
            popped_item = std::move(q_.front());
            q_.pop_front();
            pop_cv_.notify_one();
            return true;
        }

        // blocking dequeue without a timeout.
        void dequeue(T& popped_item)
        {
            std::unique_lock<std::mutex> lock(queue_mutex_);
            push_cv_.wait(lock, [this] { return !this->q_.empty(); });
            popped_item = std::move(q_.front());
            q_.pop_front();
            pop_cv_.notify_one();
        }

#endif

        size_t overrun_counter()
        {
            std::unique_lock<std::mutex> lock(queue_mutex_);
            return q_.overrun_counter();
        }

        size_t discard_counter() { return discard_counter_.load(std::memory_order_relaxed); }

        size_t size()
        {
            std::unique_lock<std::mutex> lock(queue_mutex_);
            return q_.size();
        }

        void reset_overrun_counter()
        {
            std::unique_lock<std::mutex> lock(queue_mutex_);
            q_.reset_overrun_counter();
        }

        void reset_discard_counter() { discard_counter_.store(0, std::memory_order_relaxed); }

    private:
        std::mutex queue_mutex_;
        std::condition_variable push_cv_;
        std::condition_variable pop_cv_;
        spdlog::details::circular_q<T> q_;
        std::atomic<size_t> discard_counter_{0};
    };
}  // namespace details
}  // namespace spdlog
